Final answer:
Cervical lymph nodes are located around the sternocleidomastoid muscle, which is crucial for head movement and divides the neck into anterior and posterior triangles.
Step-by-step explanation:
The cervical lymph nodes are positioned around a key neck muscle known as the sternocleidomastoid. This major muscle is responsible for the lateral flexion and rotation of the head. When the sternocleidomastoid acts unilaterally, it rotates the head; when both the left and right muscles act together, they flex the head. The role of the sternocleidomastoid is such that it divides the neck into anterior and posterior triangles when observed from the side.
Consequently, the cervical lymph nodes are located above, beneath, and posterior to the sternocleidomastoid muscle. These nodes play a pivotal role in the immune system by filtering lymph and trapping pathogens and foreign particles.